feat: TUI Phase 1 common widgets + scoring/path beads

bd-26f2: Common widgets (render_breadcrumb, render_status_bar,
render_loading, render_error_toast, render_help_overlay) + render_screen
top-level dispatch wired to LoreApp::view(). 27 widget tests.

bd-2w1p: Add half-life fields to ScoringConfig with validation.
bd-1soz: Add half_life_decay() pure function.
bd-18dn: Add normalize_query_path() for path canonicalization.

Phase 1 modules: CommandRegistry, NavigationStack, CrashContext,
TaskSupervisor, AppState with per-screen states.

172 lore-tui tests passing, clippy clean, fmt clean.

crates/lore-tui/src/state/issue_detail.rs

@@ -0,0 +1,14 @@
+#![allow(dead_code)]
+
+//! Issue detail screen state.
+
+use crate::message::{Discussion, EntityKey, IssueDetail};
+
+/// State for the issue detail screen.
+#[derive(Debug, Default)]
+pub struct IssueDetailState {
+    pub key: Option<EntityKey>,
+    pub detail: Option<IssueDetail>,
+    pub discussions: Vec<Discussion>,
+    pub scroll_offset: u16,
+}